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... ODN chain is formed by monomeric nucleotide units, each one being composed of three types of chemical components, a phosphate group, a deoxyribose and four different nitrogen bases: adenine (A) and guanine (G), the purine bases, cytosine (C) and thymine (T), the pyrimidine bases, Fig. 1. In this study homo-ODNs, composed only of one type of base in the sequence, and hetero-ODNs, formed by a mixture of different bases, were both ...
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... hydrophobicity of 10-mer ODN molecules results from the contribution of each constituent nucleotide. The hydrophobicity of each nucleotide is determined by the hydrophobicity of the aromatic base, Fig. 1, being propor- tional to its hydrophobic contact surface area. The bases, guanine, adenine, cytosine and thymine, due to their aromatic rings, adsorb onto HOPG and interaction of the π-electron system of the heteroaromatic rings of the bases with the HOPG hydrophobic surface is involved in the adsorption process. As described in the ...
Citations
This chapter describes variants of DNA sensors (genosensors) that employ electrochemical impedance signal for detecting a target DNA. In this way, the clinical diagnosticrelated sought gene or gene variant, can be very simply detected, with an electrically addressable device, and potentially, without the use of any label. Existing variants for measuring and the different formats for the assay are presented. To improve the performance of these devices, current nanobiotechnology utilizes nanocomponents, either at the transducer level or integrated in the procedure itself, to improve the detection or to amplify the signal. Carbon nanotubes and nanowires, graphene or gold nanoparticles can be used to produce or to modify transducers, fostering their electrical characteristics, or helping in the immobilization of the recognition element. Metal nanoparticles or even quantum dots may be used to improve signal to noise ratio. The chapter ends by summarizing existing applications related to clinical diagnostic, and discussing the latest trends.
Immobilization and hybridization of oligonucleotides or specific-gene PCR product (DENV-1), a conserved genomic sequence of the dengue virus, onto graphite electrode modified with poly(4-hydroxyphenylacetic acid), were carried out with success using both direct electrochemical oxidation of guanine or redox electroactive indicator ethidium bromide.Studies of oligonucleotides hybridization with the complementary target showed a decrease of both guanosine and adenosine current peaks, when compared with the peak previously obtained before the hybridization. Immobilized ssDNA, DENV-1, was hybridized with various concentrations of target DNA. The interaction between DENV-1 hybridized onto the modified graphite electrodes surface and the intercalator, ethidium bromide, was observed by differential pulse voltammetry, monitoring the current change generated to the DNA intercalator accumulated onto the modified electrode after DNA hybridization. For the determination of complementary target, the proposed method exhibited a good dynamic range (12–42 nmol L−1) and a low detection limit (7.12 nmol L−1).AFM images showed that the oligonucleotides or single-stranded DNA, DENV-1, before hybridization, had roughness values lower than the double stranded obtained after hybridization.The new surface obtained in these work, as well as the possibility of utilization of the same to monitor hybridization events is a promising strategy for the development of DNA electrochemical biosensors.
